DATABASE AND DATABASE MANAGEMENT SYSTEM Essay

1950 Words Sep 10th, 2013 8 Pages
Database
From Wikipedia, the free encyclopedia
A database is an organized collection of data. The data are typically organized to model relevant aspects of reality in a way that supports processes requiring this information. For example, modeling the availability of rooms in hotels in a way that supports finding a hotel with vacancies.
DBMS stands for "Database Management System." In short, a DBMS is a database program. Technically speaking, it is a software system that uses a standard method of cataloging, retrieving, and running queries on data. The DBMS manages incoming data, organizes it, and provides ways for the data to be modified or extracted by users or other programs. Database management systems (DBMSs) are specially
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In contrast to tree structures usually found in computer software algorithms, in this model the children point to the parents. As shown, each employee may possess several pieces of computer equipment, but each individual piece of computer equipment may have only one employee owner. 

Consider the following structure:

EmpNo

Designation

ReportsTo

10

Director

20

Senior Manager 10

30

Typist

20

40

Programmer

20



In this, the "child" is the same type as the "parent". The hierarchy stating EmpNo 10 is boss of 20, and 30 and
40 each report to 20 is represented by the "ReportsTo" column. In Relational database terms, the ReportsTo column is a foreign key referencing the EmpNo column. If the "child" data type were different, it would be in a different table, but there would still be a foreign key referencing the EmpNo column of the employees table.



This simple model is commonly known as the adjacency list model, and was introduced by Dr. Edgar F.
Codd after initial criticisms surfaced that the relational model could not model hierarchical data. The Windows
Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems.

2. Network model

Example of a Network Model.
The

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